In the past, although electric vehicles were previously developed and deployed compared with diesel and gasoline engine vehicles, electric vehicles never gained traction in car market due to abundant supply of fossil fuels. However, as concern for the environment has gathered strength, the electric vehicle market has expanded due to issues in terms of emission regulations and high oil price. In order to expand the electric vehicle market, charging infrastructures needs to be expanded, but it is not easy to supply the same level of power supply chains due to the characteristics of chargers to be installed at various places.
Accordingly, importance of basic signal processing technologies between an electric vehicle and a charger, defined according to international standards, has also gathered strength. Various standards have been defined as electric vehicle charging methods. Thereamong, a combo method is a representative method.
A DC combo (TYPE 1) method refers to a method in of integrating an alternating current (AC) connector for slow charging and a direct current (DC) connector for quick charging with one power inlet socket and is advantageous in terms of high spatial efficiency because both slow charging and quick charging are achieved via one inlet.
In the DC combo (TYPE 1) method, when one of a slow charging mode and a quick charging mode is selected in a charger, a signal is transmitted to a vehicle from the charger via a pulse width modulation (PWM) method corresponding to the selected mode. For example, in the case of the slow charging mode, a duty ratio (i.e., a ratio between H and L signals of a pulse width) of the PWM signal exceeds 5% and in the case of the quick charging mode, the duty radio of the PWM signal is about 5%.
However, there are problems in measurement of the duty ratio in that a mode cannot be accurately selected due to influence of noise in terms of a vehicle so as to cause charging failure.